- source: Getty Thesaurus of Geographic Names
- the text in this section is copied from an article in Wikipedia
Holtsville is a hamlet and census-designated place (CDP) in Suffolk County, New York, United States. The population was 19,714 at the 2010 census.
Holtsville is in the towns of Brookhaven and Islip and is the location of an IRS Processing Center (which has the lowest assigned domestic American numerical ZIP code, 00501).